The Heard Island and McDonald Islands Marine Reserve is located roughly 4,000 km southwest of the Australian mainland. It is listed as an IUCN category Ia protected area to protect the unique conservation values of the area. The island ecosystem is highly pristine – Heard Island and McDonald Islands are the only major Australian sub-Antarctic island group believed to contain no species directly introduced by humans. The marine environment supports benthic communities of slow-growing corals, sponges, barnacles, and echinoderms. The islands and their surrounding waters are major breeding habitat for seabirds and marine mammals, particularly seals. Due to the islands’ location at the confluence of major oceanographic fronts, the surrounding waters are quite rich in nutrients. They serve as a nursery area for commercial fish species, and a prime foraging area for land-based predators and cetaceans. Heard Island and McDonald Islands Marine Reserve is managed by the Australian Antarctic Division of the Department of Sustainability, Environment, Water, Population, and Communities. Because of its importance, all fishing is prohibited within the reserve boundaries.
In April 2014, the Heard Island and McDonald Islands Marine Reserve was expanded by 6200 sq km after scientific assessment of its conservation values. The expansion of the A-class, or fully protected, area as catagorized by the IUCN means it is the largest of these strictly protected marine reserves.